1. Field of the Invention
The present invention relates to a controller of a conveyance system in a production line. More particularly, the present invention relates to a controller required in controlling mobile vehicles applied in a production line of parts, such as a production line of semiconductor devices, for issuing an instruction to each individual vehicle to carry-in/out the parts to a plurality of destination arbitrarily specified among a candidate destinations.
2. Related Arts
Hitherto, there has been known a controller of a conveyance system applied to a production line of parts, a parcel distribution system or the like as disclosed in Japanese Patent Laid-open No. 63-120061, for example.
According to the technology disclosed in the aforementioned publication No. 63-120061, the controller is adapted to assign a request of carriage to an unmanned vehicle so that each work station will not become idle. At this time, it is designed to assign another request covering not only unmanned vehicles on standby and currently in operation but also the unmanned vehicle which has been already decided to be assigned within the same event. It then evaluates an access time of each of such unmanned vehicles and assigns the request to the unmanned vehicle which can be accessed first according to urgency of the carriage requests.
However, the technology described above has had a problem that it is inefficient because the carriage (carry-in/out) request or instruction issued in transporting parts from one work station to another work station is made and handled in a unit of a maximum loading capacity of one vehicle and the parts might be transported below the maximum loading capacity of the vehicle when the request is made in such a unit, as is often the case with the production line of semiconductor devices.